Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
FXUS63 KDTX 241200
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
700 AM EST Tue Jan 24 2017
LIFR ceiling/fog will persist for a few more hours during the
morning, especially while the rain is widespread and the wind is
light. Conditions are on the verge of improving well into IFR as
high pressure continues building eastward from the midwest. The
effects of light but persistent northwest wind are already being
shown over western Lower Michigan at press time and expect it will
help lift ceiling into MVFR over SE Michigan during the afternoon.
Farther west, early morning observations show stratus locked in
under the surface ridge which supports maintenance of borderline
MVFR/IFR ceiling tonight. Guidance is in good agreement that a mix
of low clouds and fog will return toward sunrise Wednesday as the
surface high settles over SE Michigan.
For DTW... Expect LIFR fog will lift to IFR ceiling during the
morning and further improve to MVFR during the afternoon. Light
northwest wind developing during the day will allow preferred SW
traffic flow operations through the day.
//DTW Threshold Probabilities...
* High for ceiling 5000 ft or less through the forecast.
* Moderate for ceiling aob 200 feet/visibility aob 1/4SM at times
through mid morning.
Issued at 245 AM EST Tue Jan 24 2017
Weak mid-level deformation and large scale ascent are keeping the
resident surface trough active with light rain showers this morning.
00z NWP and the latest RAP/HRRR give every indication in favor of a
persistence forecast through at least 18z or so as environmental
forcing/moisture variables will remain essentially unchanged.
Upstream ridging in advance of the wave emerging over the front
range this morning will eventually shunt the moisture axis east 18-
21z and shut down forcing bringing an end to rain and giving way to
overcast low clouds as the subsidence inversion strengthens and
traps low-level moisture. Clouds and rain will keep temps muted
around 40 degrees, warmer than average but less than would be
otherwise suggested by the warm airmass over the region.
Cyclogenesis is currently underway in eastern Colorado as a PV
anomaly pivots across the Front Range. This energy will rapidly
shear northeast along the northern periphery of a strong upper jet,
reaching the Great Lakes tonight. Long-standing NWP consensus at
this point for a surface low track either over or just north of the
area ensuring a stout southerly flow component at the surface for
the balance of Wednesday. Lead edge of higher theta-e airmass in the
mid-levels may force a round of rain showers across the CWA as early
as Wednesday morning before temps rise into the 40s to near 50 near
the Ohio border. Ongoing isentropic ascent will support the best
chance of stratiform rain across the far north while a rumble of
thunder or two in the warm sector is not out of the question along
the pre-frontal trough on Wednesday afternoon. Lingering deformation
supports a change over to snow as cooler air wraps into Southeast
Michigan by Thursday morning.
Developing ridge over the west coast is a high confidence feature
heading into the medium range as low pressure closes off over the
Aleutians. A period of longwave troughing expected to dominate the
remainder of the forecast period. More seasonable NW flow is shown
to be largely confluent in nature for the next several days.
Tranquil wx likely with just the occasional snow chance and highs
near average values of 30 degrees.
Weak high pressure will move over the central Great Lakes today
followed closely by the next low pressure system moving in from the
central Plains Wednesday. Light southerly wind will develop ahead of
this system which will become variable as the low moves through
central Lower Michigan and southern Lake Huron Wednesday night.
Other than a wintry mix of precipitation, this system will present
little impact on marine conditions until Thursday when it leaves
behind colder northwest wind likely reaching 30 knots across the
region. The colder and windy conditions will then last through
Friday and into the weekend.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
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